Camshaft phasers for varying the phase relationship between the crankshaft and a camshaft of an internal combustion engine are well known. A prior art vane-type phaser generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is supplied via a multiport oil control valve (OCV), in accordance with an engine control module, to either the advance or retard chambers as required to meet current or anticipated engine operating conditions.
In a typical prior art vane-type cam phaser, a controllably variable locking pin is slidingly disposed in a bore in a rotor vane to permit rotational locking of the rotor to a locking pin seat in the stator (or sprocket wheel or pulley) under certain conditions of operation of the phaser and engine. In older prior art phasers, it is desired that the rotor be locked at an extreme of the rotor authority, typically at the full retard position. To assist in positioning the rotor, it is known to incorporate a mechanical stop for the rotor and a torsional bias spring acting between the rotor and the stator to urge the rotor against the stop at the desired position for locking. Such desired position is typically at full phaser retard.
In newer prior art phasers, it is desirable that the rotor be lockable to the stator at an intermediate position in an increased rotor range of rotational authority. A known problem in such phasers is that there is no mechanical means such as a stop to assist in positioning the rotor for locking in an intermediate position; thus, locking is not reliable, and an unacceptably high rate of locking failures may occur.
What is needed in the art of phasers requiring an intermediate lock pin angle is mechanical means to advance the cam timing angle from full retard to align the lock pin with a mid-range pin seat when oil pressure is low.
It is a principal object of the present invention to cause a rotor lock pin to be properly positioned for engagement with a stator at a mid-point of the rotor's range of authority.